1. Field of the Invention
The invention relates to a connection structure between a ceramic body and an outer terminal, and particularly concerns a connection structure capable of preventing a metallic conductor from being alloyed into a soldering layer, and which is used for a ceramic package, ceramic multi-layer base and ceramic package particularly adapted for use at high frequencies.
2. Description of Prior Art
In a pin-grid array (PGA) package as shown in FIG. 3, a ceramic package body 101 has a ceramic body 111, and a surface conductor 112 made of Cu-based metal. On the surface conductor 112, an electrode layer 102 is coated which is made of Pt, Pd or Ni-Fe alloy based metal. On the electrode layer 102, an Ag-soldering layer 103 is coated to connect an outer terminal 104 to the ceramic package body 101.
However, Cu disperses into the electrode layer 102 to form a dispersion layer 102a during the sintering process. Ag melted when the outer terminal 104 is connected to a the soldering layer 103 disperses into the surface conductor 112 located in a throughhole, as seen at arrow X in FIG. 3. The Ag thus dispersed amalgamates with the copper to form spherical body so as to lead electrical bodies, which can disrupt the electrical connection.
This holds true in the case in which the surface conductor is made of Au-based metal instead of Cu-based metal.
It is appreciated that instead of Cu the surface conductor 112 may be made of Pt or Pd which do not easily amalgamate with Ag, but these metals are not in general use since they are expensive and have a high electrical resistance of about ten times that of Cu and Au.